Nitride semiconductor devices have physical properties suitable as high-breakdown-voltage high-speed electronic devices and are expected to be applied to, for example, server systems. There are high-breakdown-voltage semiconductor devices including substrates composed of, for example, silicon (Si) and silicon carbide (SiC), which are called vertical nitride semiconductor devices. Such a vertical nitride semiconductor device includes a p-type semiconductor region formed in the surface of the semiconductor layer by ion implantation of p-type impurities for the purpose of suppressing a decrease in the reverse breakdown voltage due to electric field concentration in a region of the semiconductor layer, the region being located at the interface between the semiconductor layer and the insulation layer, and increasing the surge current capacity. The p-type semiconductor region is called a junction termination extension (JTE) structure.
Examples of existing JTE structures include a multizone structure and a guard ring structure. The multizone structure is formed by ion implantation of p-type impurities into a compound semiconductor layer such that the concentration of the p-type impurities gradually decreases from the active area toward the dicing area. The guard ring structure is formed by ion implantation of p-type impurities into a compound semiconductor layer such that the implantation interval of the p-type impurities is changed from the active area toward the dicing area. JTE structures are thus formed by ion implantation of p-type impurities to gradually reduce electric field concentration.
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